LiteBIRD, the next-generation cosmic microwave background (CMB) experiment, aims for a launch in Japan’s fiscal year 2032, marking a major advancement in the exploration of primordial cosmology and fundamental physics. Orbiting the Sun-Earth Lagrangian point L2, this JAXA-led strategic L-class mission will conduct a comprehensive mapping of the CMB polarization across the entire sky. During its 3-year mission, LiteBIRD will employ three telescopes within 15 unique frequency bands (ranging from 34 through 448 GHz), targeting a sensitivity of 2.2 μK-arcmin and a resolution of 0.5° at 100 GHz. Its primary goal is to measure the tensor-toscalar ratio r with an uncertainty δr = 0.001, including systematic errors and margin. If r ≥ 0.01, LiteBIRD expects to achieve a > 5σ detection in the ℓ = 2–10 and ℓ = 11–200 ranges separately, providing crucial insight into the early Universe. We describe LiteBIRD’s scientific objectives, the application of systems engineering to mission requirements, the anticipated scientific impact, and the operations and scanning strategies vital to minimizing systematic effects. We will also highlight LiteBIRD’s synergies with concurrent CMB projects.
In the 1990s COBE/FIRAS showed that the CMB spectral energy distribution is close to a perfect blackbody with tiny departures, ΔI/I ≃ 10−5, referred to as spectral distortions, that encode information about the full thermal history of the Universe. High-precision spectroscopy of the CMB is one of the three themes identified by the ESA Voyage 2050 programme to explore the early Universe. The BISOU (Balloon Interferometer for Spectral Observations of the primordial Universe) project is a pathfinder of a future space mission dedicated to the absolute measurement of the CMB spectrum. With the instrument and sky models developed in [6], we examine the influence feasibility of detecting the y-distortion monopole (probing the hot gas in the Universe).
The BISOU (Balloon Interferometer for Spectral Observations of the primordial Universe) project studies the viability and prospects of a balloon-borne spectrometer, pathfinder of a future space mission dedicated to the measurements of the CMB spectral distortions. A balloon concept based on a Fourier Transform Spectrometer, covering a spectral range from about 90 GHz to 2 THz, adapted from previous mission proposals such as PIXIE and FOSSIL, is being studied and modeled. Taking into account the requirements and conditions of balloon flights, we present here the instrument concept together with the results of a CNES Phase 0 study. We forecast a first detection of the CMB Compton y-distortion monopole with a signal-to-noise ratio of at least 5. We also present the future plan and work that will be the subject of a recently awarded two-year Phase A study.
The BISOU (Balloon Interferometer for Spectral Observations of the Universe) project studies the viability and prospects of a balloon-borne spectrometer, pathfinder of a future space mission dedicated to the measurements of the CMB spectral distortions, while consolidating the instrumental concept and improving the readiness of some of its key sub-systems. A balloon concept based on a Fourier Transform Spectrometer, covering a spectral range from about 90 GHz to 2 THz, adapted from previous mission proposals such as PIXIE and FOSSIL, is being studied and modelled. Taking into account the requirements and conditions of balloon flights (i.e. residual atmosphere, observation strategy for instance), we present here the instrument concept together with the results of the CNES phase 0 study, evaluating the sensitivity to some of its potential observables. For instance, we forecast a detection of the CMB Compton y-distortion monopole with a signal-to-noise ratio of at least 5.
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